1. Field of the Invention
The present invention relates generally to systems and methods for processing waste material, and more particularly to such systems and methods which may not only effect the sterilization and optionally, disinfection, of waste material such as medical (also known as “red bag”), food, disposable diapers, and other types of waste, but also reduce the volume of such waste material, and dispose of water soluble polymeric or fibrous waste material.
2. Statement of the Prior Art
Waste management evolved in the latter part of the twentieth century into an industry of considerable importance, as societal and environmental attention had focused on the conventional processes by which waste has to date been handled for disposal. These conventional waste disposal processes included incineration, dumping at sea, and burial in landfills. Each of these processes, however, is encumbered by significant societal and environmental disadvantages and regulatory restrictions.
Incineration is objectionable due to its attendant chemical and particulate pollution of the atmosphere and surrounding locales. Further, these pollutants can be transported over great distances by prevailing winds, thereby extending the scope of environmental impact beyond the immediate locale of the incinerator. Waste disposal in the oceans is objectionable due to its adverse environmental impact on sea life and coastal shores. Landfills are objectionable due to their attendant spatial demands, offensive odors, contamination of ground water and potential for production of hazardous substances arising from the mixing and interaction of buried materials.
Spatial considerations are especially prevalent in urban centers, where population growth has resulted in suburban expansion to locations well outside of the urban center, necessitating in some instances in the relocation of existing landfills and the creation of costly new landfills at locations geographically remote from the centers they serve. Disposable diapers, for example, have proven to be an increasing problem for municipal disposal.
Additional waste disposal problems arise in view of the type of waste that is to be disposed. For example, special precautions are required for the disposal of biological and medical waste due to the overwhelming concern for preventing the creation and/or spread of infectious disease. Further concerns arise due to the presence of extremely sharp medical instruments such as needles, knives, and broken glass containers that can cut or lacerate the skin of personnel and animals with which the waste comes in contact, thereby presenting both a risk of physical harm and biological contamination. For these reasons, such waste is typically thermally or chemically treated and buried in dedicated medical waste disposal facilities. The treatment should be of a type that renders the waste biologically neutral or inert.
Sterilization can typically be accomplished by any one of a variety of prescribed chemical and non-combustion thermal treatment regimens, as well as incineration or autoclaving. Autoclaving provides for exposure of the waste to heat at upwards of 250° F. (121° C.) at 15 pounds per square inch (“PSI”) for 15-40 minutes. While sterilization can be accomplished in both dry air and steam environments, steam autoclaving is generally preferred due to its greater penetrating capabilities (especially important for sterilizing “soft” waste such as textiles and gauze) and its lethality via the process of denaturation. Longer periods are used to assure steam penetration of heavy, fluid-absorbable loads. Faster processing can be accomplished for some waste materials by increasing temperature and pressure. However, a significant disadvantage of steam autoclaving without reducing the size of the material is its failure to assure complete penetration of the waste and its exposure to the heat contained within the water vapor. Further disadvantages include the tendency for autoclaves (both steam and dry) to stratify and to trap comparatively cool air in pockets, thereby precluding sterilization. In addition, the waste is neither reduced in volume or in mass; instead, mass can increase in some instances (i.e., textiles and gauze) due to the absorption of water vapor, thereby exacerbating the problem of waste disposal referenced above.
A popular alternative to autoclaving is chemical disinfection. Chemical sterilization generally provides for exposure of the waste material to an antiseptic solution such as liquid chlorine for a prescribed time interval; however, the use of chemical sterilizing agents presents disposal problems for the liquid following waste treatment due to the toxicity of chlorine and other antiseptic solutions.
In view of the foregoing, there is a pressing societal need to not only reduce the volume of waste material that is produced, but also to more effectively and efficiently process the waste so that it has a diminished environmental impact. This need is especially pressing in instances where waste is produced in bulk, as can occur in hospitals, clinical laboratories, research facilities, nursing homes, restaurants, and the like.
While efforts are being undertaken to reduce waste production, these efforts alone will not eliminate the various problems associated with waste disposal, particularly in the medical and dental industries, where single patient use (i.e., non-reusable) surgical instruments have gained widespread acceptance due to concerns over spread of the family of hepatitis viruses and HIV.
Moreover, it would be preferable to provide systems and methods for processing waste material at a lower cost, environmentally and economically.